Monochromatic beam application in medical imaging and material analysis.

摘要

Polycapillary optics can be employed as efficient low pass devices in conjunction with simple absorption filters to produce narrow band radiation from conventional broadband x-ray tube sources. Narrow band filtration is adequate for low-resolution powder diffraction without a monochromaor. Polycapillary optics can collect a large solid angle of x-rays from a laboratory point source and form intense focused beams, for powder diffraction and micro x-ray fluorescence (MXRF).; Focused monochromatic micro beams were generated from low power sources using doubly curved crystal (DCC) optics. These optics provide an enabling technology for new portable, remote, and in situ application of monochromatic x-rays for composition and structure analysis. Femtogram sensitivity for surface contamination was achieved.; Polycapillary optics can be used for a variety of imaging applications. Placing the optic after the object to be imaged provides very efficient rejection of Compton scatter because of the low angular acceptance of the capillaries. Scatter fraction and contrast data performed with energy sensitive and imaging detectors were in good agreement. A detailed calculation for comparing these broadband and monoenergenic-input scatter fraction data was performed. The agreement validates predictions of the effect of input spectrum on contrast of an image at different energies.; The potential use of polycapillary optics to provide extraordinarily high spatial resolution imaging of radioactive sources for a new generation of gamma cameras was investigated. A series of images from 125I brachytherapy seeds in Lucite phantoms display resolution better than 0.l mm and signal to noise ratios in excess of a factor of 10.; For applications that would benefit from more monochromatic or more parallel input beams, polycapillary collimating optics can be used to collect divergent radiation and redirect it towards a monochromatizing crystal to produce orders of magnitude higher diffracted intensity than from pinhole collimation. The implementation of high contrast monochromatic and refractive index imaging with a very low power source has been demonstrated.